The invention relates generally to video graphics processing and more particularly to a method and apparatus for accumulation buffering in a video graphics system.
Computer displays and other high resolution display devices such as high definition televisions (HDTV), projectors, printers, plotters, and alike, present an image to the viewer as an array of individual picture elements, or pixels. The individual pixels are each given a specific color, which corresponds to the color of the image at the location of the particular pixel. If the pixels are closely spaced, the viewers visual system performs a filtering of the individual pixel colors to form a composite image. If the partitioning of the image into individual pixel elements is performed properly, and the pixels are close enough together, the viewer perceives the displayed array of pixels as a virtually continuous image. Despite the viewers visual filtering, the viewer remains sensitive to aberrations in the image, and video graphics systems must be designed to minimize these aberrations.
In order to avoid one potential source of visual aberrations, accumulation buffering is used to avoid aliasing in the graphics image display. In accumulation buffering, multiple images are rendered and then combined in an accumulation buffer where the multiple images are blended. Utilization of accumulation buffering is an anti-aliasing technique that is well known in the art.
Because accumulation buffering requires multiple images to be rendered prior to their combination to produce a resultant image, a large number of memory accesses and blending operations are performed for each image that is included in the accumulation buffer. In some instances, some of these memory operations and blending operations are unnecessary as new pixel information may not be generated for every pixel during the rendering of an image. As such, blending all of the pixels for a particular image with the information in the accumulation buffer may not change the accumulated values for all of the pixels in the accumulation buffer.
Therefore, a need exists for a method and apparatus that supports accumulation buffering in a video graphics system that reduces the number of memory operations and blending operations necessary to produce the resultant accumulated image.